A vast amount of experience in the technology of “ground or surface effect” for marine vehicles occurred during the half century 1950–2000. During that time, the hovercraft came into being in its birthplace in England and throughout the world. Both commercial and military uses benefited from these craft that typically operated at speeds up to 50 knots in littoral sea states. That history has been covered in the early chapters of this book (see Chapter 1 and Chapter 2 and throughout) as data from that era was used in the technical development chapters. A derivative of the hovercraft that became known as the surface effect ship enjoyed significant development during the two decades 1960–1980 most intensely in the US where speeds approaching 100 knots were achieved. That history has occupied many chapters in this book. The development of the aerodynamic air cushion craft has actually covered a much longer period from the original work by Prandtl and Wieselsberger in the 1920s to the present day. The most developed work in terms of operational craft was that done in Russia in the 1960–1990 period when such craft operated at speeds in excess of 200 knots (see Chapter 11).

Each of those key periods produced significant work in theories of ground effect, substantial experimental data and many operational vehicles. Copious references to that work appear in the various chapters and used in the development of the simple theories provided here in the understanding of a “100 knot at sea capability”.

It is in the critical period, 1960–1980, when the most intense and fruitful development was undertaken to achieve a practical 100 knot capability, that the stumbles began to occur. They can be grouped under the two main headings of (1) unresolved technical problems and (2) neglecting to follow well-established R&D management practices. These issues have been addressed in the preceding chapters. It is believed that it would have been possible to have achieved a high speed marine craft for practical missions capability within the time and money expended if a few simple established procedures had been followed.